High Sensitivity and Rapid Response Optomechanical Uncooled Infrared Detector From Self-Assembled Super-Aligned Carbon Nanotubes Film

Abstract

The optomechanical uncooled infrared (IR) detector, characterized by a straightforward manufacturing process and sensitivity comparable to photonic detectors, employs bi-material microcantilevers as individual pixels. The detector’s key performance parameters are thermomechanical sensitivity and time constant, which are directly proportional to the coefficient of thermal expansion (CTE) mismatch and thermal mass of the two materials. Carbon nanotubes (CNTs), which exhibit thermal contraction axially, have a CTE value of $- 11 \times 10 ^{-6}\,\,\text{K}^{-1}$ around room temperature. When combined with metals, such as gold, which have a positive CTE, it is possible to create bi-material pixels with superior thermomechanical sensitivity. The low thermal mass nature of CNTs inherently endows the pixels with a rapid thermal response. To realize an optomechanical IR detector based on super-aligned CNTs, a microfabrication process was developed that incorporates a liquid-induced CNT self-assembled step. Theoretical analyses indicate that the thermomechanical sensitivity and response speed are doubled compared to traditional ceramic-metal based photomechanical uncooled IR detectors. The experimental results are in good agreement with the theoretical values, demonstrating a measured time constant and thermomechanical sensitivity of 62 ms and $0.466~\mu \text{m}$ /K, respectively. This design offers a viable path towards the development of high-performance uncooled IR detectors, facilitated by the integration of super-aligned CNTs. [2024-0011]